regulator: Fix s5m8767_set_voltage_time_sel calculation value

In the s5m8767_set_voltage_time_sel function, divisor unit is wrong.
ramp_delay is usec unit. So 1000 should be multiplied.

Signed-off-by: Sangbeom Kim <sbkim73@samsung.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>